In many different circuits, it is frequently necessary to detect and measure very small differential voltages which are present on leads concurrently with relatively large common mode voltages. For example, in scientific instrumentation, signals in the microvolt and tens of microvolt range must frequently be measured at remote locations. Due to capacitive and inductive coupling, AC signals as large as several volts may be coupled into the signal leads from 60 Hz power line. Also, there may be a voltage drop between the transducer ground and ground at the measuring site which contributes to the common mode voltage. Differential amplifier circuits which provide high common mode rejection and low noise are therefore useful circuits.